Extend this class to implement google sign-in. setSilentSignIn(false) to stop silent sign in http://bit.ly/1kVJAHZ. @OverRide handleGoogleSignInResult.

GoogleSignInBaseActivity.java

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import com.google.android.gms.auth.api.Auth;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.auth.api.signin.GoogleSignInResult;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.OptionalPendingResult;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;

public abstract class GoogleSignInBaseActivity extends AppCompatActivity implements
        GoogleApiClient.OnConnectionFailedListener {

    protected GoogleApiClient mGoogleApiClient;

    protected static final int RC_SIGN_IN = 9001;
    private static final String TAG = "GoogleSignInBaseActivity";
    private boolean silentSignIn = true;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                .requestEmail()
                .build();

        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .enableAutoManage(this /* FragmentActivity */, this /* OnConnectionFailedListener */)
                .addApi(Auth.GOOGLE_SIGN_IN_API, gso)
                .build();
    }

    @Override
    public void onStart() {
        super.onStart();
        if (silentSignIn) {
            OptionalPendingResult<GoogleSignInResult> opr = Auth.GoogleSignInApi.silentSignIn(mGoogleApiClient);
            if (opr.isDone()) {
                Log.d(TAG, "onStart: opr.isDone()");
                handleGoogleSignInResult(opr.get());
            } else {
                Log.d(TAG, "onStart: opr not done");
                opr.setResultCallback(this::handleGoogleSignInResult);
            }
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        setSilentSignIn(false);
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Log.d(TAG, "onConnectionFailed: " + connectionResult);
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        Log.d(TAG, "onActivityResult: " + data);

        // Result returned from launching the Intent from GoogleSignInApi.getSignInIntent(...);
        if (requestCode == RC_SIGN_IN) {
            GoogleSignInResult result = Auth.GoogleSignInApi.getSignInResultFromIntent(data);
            handleGoogleSignInResult(result);
        }
    }

    protected void googleSignIn() {
        Intent signInIntent = Auth.GoogleSignInApi.getSignInIntent(mGoogleApiClient);
        startActivityForResult(signInIntent, RC_SIGN_IN);
    }

    protected void googleSignOut(ResultCallback<Status> callback) {
        Auth.GoogleSignInApi.signOut(mGoogleApiClient).setResultCallback(callback);
    }

    protected void googleRevokeAccess(ResultCallback<Status> callback) {
        Auth.GoogleSignInApi.revokeAccess(mGoogleApiClient).setResultCallback(callback);
    }

    abstract handleGoogleSignInResult(GoogleSignInResult result);

    protected void setSilentSignIn(boolean bool) {
        silentSignIn = bool;
    }

}